The goal of the proposed studies is to understand the basic principles of enhancer-promoter interactions in complex genetic loci with particular emphasis of the Abd-B region of the Drosophila bithorax complex (BX-C). The Abd-B gene contains 5 parasegmental-specific regulatory regions, or infra abdominal (iab) regions that span over approximately 100 kb of DNA. Two class of specialized DNA elements may might regulate enhancer- promoter interaction and to keep neighboring cis regulatory regions separates; augmenter DNA might facilitate enhancer-promoter interaction over long distances. An insulator DNA element, Front abdominal-7 (Fab-7), has been characterized between iab-6 and iab-7. The specific aims of the proposed study is to identify trans-acting factors for Fab-7 through genetic screens, and to identify and characterize augmenter elements that facilitate long range enhancer promoter interactions.